Unit Scaling Prefixes: (was Birthday Wish)

[brian whatcott <inet@INTELLISYS.NET>]

At 17:51 4/11/99 -0500, J.D Patterson wrote:
> On Sat, 10 Apr 1999, brian whatcott wrote:
>
> > I know a person who claims to have an engineering degree who refers
> > to a term like "33MHz" as thirty three millihertz.
>
> Be careful, often times in engineering, M is used instead of m or mu for
> milli- or micro-.  I'm not sure why this is, but I do know that it is
> done.  Many capacitors are labelled 'MF' for microfarads.
>
>        J. Douglas Patterson

Although I deny that engineers use M for milli- or micro-, I acknowledge
 that electronic components are often mismarked in this way.
So there is virtue in Douglas's warning. In these cases, context can
provide guidance. But these days, capacitors can take values between
picofarads to farads and all points between. So the old rule of thumb about
a mismarked
"mF" or "MF"  more likely meaning microfarad (uF) than millifarad (mF) has
lost its strength. But because there is no instance of a megafarad capacitor
 ever (yet), one can at least discard that possibility.

  But in measuring frequency, I have seen reference to measurements in
millihertz just once, while megahertz tags are legion.
There was a reference in the splendid French-U.S work on resolving
breathing mode frequencies of the Sun, that I have mentioned before.
 They used the Fourier transform of an unbroken train of solar observations
of the Doppler shift of some hyperfine Sodium line taken in, I think, the
Antarctic.

 So as a sweeping generalization, I'd say measurements in millihertz are
to be found rarely among physicists, and not often from engineers, where
the context is generally informative.

Brian
brian whatcott <inet@intellisys.net>
Altus OK